Control for spill ports for freepiston units



Jan. 4, 1949. D. M. POOLE 2,458,198

CONTROL FOR SPILL PORTS FOR FREE-PISTON UNITS Filed April 15, 1944INVENTOR oAvuo M. POOLE mam.

ATTORNEY d) N n Patented Jan. 4, 1949 UNITED STATES PATENT OFFICECONTROL FOR SPILL PORTS FOR FREE- PISTON UNITS Application April 15,1944, Serial No. 531,308

This invention relates to a free-piston engineand-compressor unit andparticularly to a control for the spill ports by which the effectivevolume of the compressor is adjusted.

The copendinapplication of Cooper, Serial No. 531,301, filed April 15,1944, describes a freepiston unit, the compressor cylinder of which hasa number of rows of openings forming spill ports through which a part ofthe air in the compressor cylinder is discharged. A featureof thisinvention is an arrangement for controlling the ports.

When the unit is adapted for aircraft use, and therefore, subject tosubstantial variations in intake pressure, the unit can best be adaptedto these variations by successive closing of the rows of ports. Afeature of this invention is an arrangement by which the rows of portsmay be individually and successively controlled.

Another feature of this invention is a control for the ports which iscompact and will not seriously increase the space requirement for theunit. Another feature is the control of the ports by an axially movableband extending around the compressor cylinder.

Other objects and advantageswill'be apparent 25 from the specificationand claims, and from the accompanying drawings, which illustrate anembodiment of the invention.

Fig. 1 is a sectional view through a free-piston unit.

Fig. 2 is a fragmentary view of the activating mechanism for the innerbands.

The unit shown includes an engine cylinder having reciprocating pistonsl2 and I4 to which compressor pistons 16 and I8 in cylinders 20 and 22are integrally connected. Sleeves 24 and-26.

attached to the compressor pistons complete the reciprocating pistonassemblies. The sleeves in combination with stationary pistons 28 and toform air spring cylinders.

The piston assemblies are moved apart by the burning of fuel injectedinto engine cylinder It through one or more nozzles 32. Air compressedin the air spring cylinders on the power stroke returns the pistonassemblies. The assemblies are always maintained at equal distances fromthe center of the engine cylinder by a linkage, not shown.

Intake manifold 62, which extends around the compressor and enginecylinders conducts air to intake valves 66 in the heads of thecompressor cylinders, through which air alternately enters opposite endsof the cylinders. The compressed air leaves the cylinder throughdischarge valves 48, also at opposite ends of the compressor cyl- 8Claims. (Cl. 230-56) inders and passes into a central scavenge chamber48 and end chambers 50 and 62. These These chambers may beinterconnected by a scavenge manifold, not shown.

Compressed gas from the scavenge chambers enters engine ports 54 and 56which are uncovered by pistons l2 and M at the end of the power stroke,thereby permitting air to be blown through the engine cylinder. Gas andair in the engine cylinders are discharged through exhaust ports 58 intoexhaust manifold 60.

Each compressor cylinder has a number of axially spaced rows of spillports 62 which permit discharge of air from the cylinders withoutcompression. The rows of ports are controlled by 2g and an inner band65-50 that the inner and outer end rows may be closed before the otherrows, and, by selective movement of the bands, the rows or ports may beclosed or opened in sequence from opposite ends of the cylinder;

If the unit is used in aircraft, and is designed for altitude operation,the bands are moved so that all the rows of ports are open at sea l v l,

and only a small volume of gas is compressed. As

thedensity of the air decreases (at altitude) one so or more of the rowsof ports may be successively closed, beginning with the end rows toincrease the efiective volume of the compressor. The several rows ofports permit adaptation of the compressor to substantially any altitudeor to any air density.

The bands may be moved manually or they may be moved mechanically. Forexample, as shown, the outer bands 54 may have inwardly projecting rods58 carrying, on their inner ends, pistons i0 in a .cylinder 12. Forclosing the spill ports, fluid under pressure enters the outer ends ofthe cylinder through a pipe l4 and fluid exhausts through a central pipe16. If desired, a control mechanism may be used for admitting fluidselectively through pipe 14 or it.

A similar control device may be used for moving the inner bands, thedevice operating independas the pistons are urged apart to close theinner rows of ports successively from the inner ends of the compressorcylinders.

It is to be understood that the invention is not limited to the specificembodiment herein illustrated and described, but may be used in otherways without departure from its spirit as defined by the followingclaims.

I claim:

1. A free-piston unit including a compressor cylinder and a pistontherein, said cylinder having a cylindrical wall with atleast one rowof! circumferentially arranged ports extending therethrough, and a bandsurrounding. engageable with. and movable on the outer surface'of said 5inders having a cylindrical wall having a number cylindrical wall toclose or operrsaid ports.

2. A free-piston unit including a compressor cylinder and a pistontherein, said cylinder having a cylindrical wall with at least one rowof circumferentially arranged ports extending therethrough, and a bandsurrounding. enga in with, and movable axially on the outer surface ofsaid cylindrical wall for opening or closing the 3. A free-piston u'nitincluding a compressor cylinder and a piston therein, said cylinderhaving a cylindrical wall with a number of axially spaced rows of portsextending through the wall and arranged circumferentially therein, andat least' one band engageabie with and movable axially on the outersurface of said cylindrical wall for opening or closing the rows ofports-in a predetermined sequence. y

' 4. A free-piston unit including a' compressor cylinder and a pistontherein, said cylinder hav ing a cylindrical wall with a number ofaxially spaced rows of ports extending through the wall 85 and arrangedcircumferentially therein, at' least one band engageable with andmovable axially on the outer surface or said cylindrical wall foropening or closing the rows'of ports-in a prede t'e'rmined sequence, andmeans for moving said 40 hand axially along the outer surface of the cylinder wall.

s. A free-piston unitincluding an engine cylinder, opposed pistons inthe cylinder, compressor pistons moving with the engine-pistons, andopposed compressor cylinders for said compressor pistons located atopposite ends of' the engine cylinder, said compressor cylinders eachhaving a number of axially spaced rows of ports extending through thecylinder, each row extending circumferentiallyaround the cylinder, a'closure means on the outer surface oi each cylinder mov-Q able to closethe rows of] ports. and means for moving-the closure means on theopposed com pressor cylinders simultaneously.

- 8. A free-piston unit including cyl- 4 inder, opposed pistons in thecylinder, com pistons moving with the engine pistons, and compressorcylinders for said compressor pistons located at opposite ends of the enine cylinder, each of said compressor cylinders having a cylindricalwall having a number 0t axially spaced rows of ports. each row extendingcircumferentially around the compressor cylinder, and a band extendingaround each compressor cylinder and movable to open or close the ports.

7. A free-piston unit including an engine cylinder, opposed pistons inthe cylinder, compressor pistons moving with the engine pistons, andcompressor cylinders, each of saidcompressor cylof axially spaced rowsof ports extending therethrough, each row extending circumferentiallyaround the compressor cylinder, and a band extending around eachcompressor .cylinder and movable axially on the compressor cylinder foropening or closing the ports.

8. A free-piston unit including an engine cylinder, opposed pistons inthe cylinder, compressor pistons moving with the engine pistons, andcompressor cylinders, said compressor cylinders each o axially on thecompressor cylinder for opening or closing rows 01 portssuccesslvely.DAVID M. room.

.REFERENCES crrsn The following references, are of record in the dle ofthis patent:

UNITED STATES PATENTS Number Name Date 877,492 Doelling Jan; 28, 19081,481,358 Dwyer Jan. 22, 1924 1,579,782 Riesner Apr. 8, 1926 1,889,787Trumble Aug. 2, 1932 2,018,613 Pescara Oct. 8. 1935 2,064,976 JanickeDec. 22, 1936 2,076,258 'Witkrewicz Apr. 6, 1937 2,108,890 Janicke- Feb.22, 1938 2,134,920 Kadenacy Nov. 1, 1938 2,189,497 Pescara Feb. 6, 19402,282,582 Cole May 12, 1942 2,319,588 Sundermanet al. May'18, 1943FOREIGN PATENTS Number Country Date 68 168,337 Germany 1903 237,170Germany 1910

